6 CIRCULAR 659, U. S. DEPARTMENT OF AGRICULTURE 



testers have been devised. The one most commonly used is that de- 

 veloped by Magness and Taylor (17), which measures the 'pressure re- 

 quired to force a plunger seven-sixteenths of an inch in diameter into 

 the flesh of the apple to a distance of five-sixteenths of an inch after 

 paring off the skin. Haller (7) has presented the results of a long series 

 of investigations on the use of the pressure test on apples and other 

 fruits. Pressure-test records have been transposed into the ordinarily 

 accepted commercial designations of "hard," "firm," "firm ripe," and 

 "ripe" by Haller, Lutz, and Mallison (£). The foregoing publications 

 give details on the application and limitations of the pressure test. 



TISSUE CHARACTERISTICS 



As apples mature and ripen starch and astringent constituents de- 

 crease. Tests for starch with an iodine and potassium iodide solu- 

 tion have proved unreliable because of the variability in starch among 

 individual fruits of practically the same degree of maturity and because 

 of variability due to heavy and light crops and seasonal growing condi- 

 tions. Familiarity with the astringent taste of apple tissue is a guide to 

 picking maturity of varieties like Delicious and its red bud sports; satis- 

 factory maturity is not acquired until sensations from astringency are 

 practically absent. This is usually associated with loss of toughness 

 in tissue texture. Water core kuthe tissue is a very important considera- 

 tion in determining when to pick certain varieties. Investigations by 

 Brooks and Fisher (4) show that water core develops first in fruit ex- 

 posed to direct sunshine on the south and west sides of trees. Conse- 

 quently, apples from these parts and the tops of trees should be examined 

 for water core. As maturity advances water core increases; this gen- 

 erally is a signal that the fruit is passing the optimum state of picking 

 maturity and may become subject to internal breakdown early in 

 storage. 



GENERAL RECOMMENDATIONS FOR PICKING 



Because no single criterion is entirely dependable for determining 

 when to pick, the grower usually must base his decision on a number of 

 factors. A tentative date on which to start picking a variety should be 

 established on the basis of the number of days from full bloom. As this 

 date approaches the fruit should be watched closely. If the fruit shows 

 signs of advanced maturity, such as a break in the ground color, a tend- 

 ency of sound fruit to drop, water core, and loss of astringency and 

 bitterness, the picking date should be advanced. On the other hand, 

 if the apples are still green in color, hard, tough or woody in texture, 

 and astringent or bitter in taste, it may be advisable to delay picking 

 beyond the tentative date. The date of picking will probably need to 

 be advanced with a light crop or exceptionally warm weather after 

 bloom; conversely, a heavy crop or cold weather after bloom is likely 

 to delay the date of picking. 



WHEN TO PACK APPLES 



Ideally, apples should be packed and stored or shipped immediately 

 after being picked. Danger of blue mold infection is less if this can 

 be done because injury to the apples during the packing operations is 

 much less likely if the fruit is hard than if it has begun to soften. Scald 



